The soil injection technology using an expandable polyurethane resin is one of the most efficient modern techniques that have been actively used in recent years for soil stabilization and foundations lifting. There are many advantages of using this technology, such as the rapid and strictly controlled process of lifting foundations, ease of use, high mobility and the lightweight of injectable foaming resin in addition to the independence of the physical and mechanical properties of resin from groundwater level, which allow the application of the proposed technology in a variety of geotechnical conditions and projects of various specificities. As part of the study of this technology in the world, very few theoretical and practical studies have been conducted. Most of these studies are focused mainly on the process of raising the foundations and monitoring of this technology. Thus, various monitoring methods have been developed around the world to control the injection process and to provide adequate tracking and a sufficient degree of visualization of the foundations lifting process in various geotechnical situations. Nevertheless, the application of this technology in the field of the soil stabilization and foundation strengthening has so far had certain limitations due to the lack of sufficient scientific theoretical and experimental justifications for the combined behavior of the composite (soil-resin) and the absence of an advanced calculation method, that allows predicting the altered characteristics of the treated soil massive after its injection by the expandable resin. The article demonstrates the results of a developed calculation method for predicting the averaged characteristics of the strengthened massive of a soil base after its injection by an expandable resin, based on theoretical and practical evidence obtained as a result of field and laboratory experiments, utilizing different approaches of the finite element method. The obtained by the developed calculation method results have been compared to the results of in-situ plate load tests obtained from field experiments without the injection of the resin and after its inclusion into the massive of the investigated soil to verify its accuracy.